import time
import smbus
import logging

BUS = smbus.SMBus(1)
LCD_ADDR = 0x27
BLEN = 1 #turn on/off background light

def turn_light(key):
    global BLEN
    BLEN = key
    if key ==1 :
        BUS.write_byte(LCD_ADDR ,0x08)
        logging.info('LCD executed turn on BLight')
    else:
        BUS.write_byte(LCD_ADDR ,0x00)
        logging.info('LCD executed turn off BLight')

def write_word(addr, data):
    global BLEN
    temp = data
    if BLEN == 1:
        temp |= 0x08
    else:
        temp &= 0xF7
    BUS.write_byte(addr ,temp)

def send_command(comm):
    # Send bit7-4 firstly
    buf = comm & 0xF0
    buf |= 0x04               # RS = 0, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)
    
    # Send bit3-0 secondly
    buf = (comm & 0x0F) << 4
    buf |= 0x04               # RS = 0, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

def send_data(data):
    # Send bit7-4 firstly
    buf = data & 0xF0
    buf |= 0x05               # RS = 1, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)
    
    # Send bit3-0 secondly
    buf = (data & 0x0F) << 4
    buf |= 0x05               # RS = 1, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

def init_lcd():
    try:
        send_command(0x33) # Must initialize to 8-line mode at first
        time.sleep(0.005)
        send_command(0x32) # Then initialize to 4-line mode
        time.sleep(0.005)
        send_command(0x28) # 2 Lines & 5*7 dots
        time.sleep(0.005)
        send_command(0x0C) # Enable display without cursor
        time.sleep(0.005)
        send_command(0x01) # Clear Screen
        logging.info('LCD init over')
        BUS.write_byte(LCD_ADDR ,0x08)
        logging.info('LCD turning on BLight')
    except:
        return False
    else:
        return True

def clear_lcd():
    send_command(0x01) # Clear Screen

def print_lcd(x, y, str):

    if x < 0:
        x = 0
    if x > 15:
        x = 15
    if y <0:
        y = 0
    if y > 1:
        y = 1

    # Move cursor
    addr = 0x80 + 0x40 * y + x
    send_command(addr)
    
    for chr in str:
        send_data(ord(chr))

def clock():
    while True:
        _time = time.strftime("%Y-%m-%d", time.localtime())
        print_lcd(0, 0, _time)
        _time = time.strftime("%H:%M:%S", time.localtime())
        print_lcd(8, 1, _time)
        time.sleep(1)

if __name__ == '__main__':
    init_lcd()
    clock()